The instant invention relates to textile manufacturing and processing and more particularly to an apparatus for treating fabrics for shrinkage.
It has long been recognized that many fabrics must be treated for shrinkage before they can be effectively used for garments or other items. This is largely because of the fact that yarns and fibers normally undergo a certain amount of stretching when they are woven or knitted into fabrics so that initially many knitted or woven fabrics comprise fibers which are in stretched and unrelaxed conditions. When these fabrics are subsequently exposed to processes such as washing or dyeing, the yarns and fibers thereof tend to return to their prestretched or relaxed conditions, and this causes shrinkage of the fabrics which may be highly irregular or uneven in many cases. Further, if these fabrics are made into garments, additional uneven shrinkage may occur when the garments are laundered. Accordingly, it has proven to be necessary to provide some means for treating fabrics for shrinkage before they are formed into garments so that the garments are not ruined or at least substantially distorted by subsequent shrinkage.
The U.S. Patent to Wehrman U.S. Pat. No. 3,007,223 discloses a "Process and Apparatus for Controlling Shrinkage and Otherwise Improving the Characteristics of Tubular Fabrics" and represents the closest prior art to the apparatus of the instant invention of which the applicants are aware. The device disclosed in this patent is operative for compressing tubular fabrics utilizing a pair of adjacent rollers having belts thereon and a freely floating form having a forward portion of reduced thickness which extends into the nip or gap between the rollers. A tubular fabric is received on the form so that the form is disposed in the tubular interior of the fabric, and, as a result, a single thickness or layer of fabric is interposed between each side of the form and the adjacent roller. During the operation of the apparatus, the rollers cooperate to draw the fabric and the form into the nip between the rollers. However, since the form is dimensioned so that it cannot fit between the rollers, the fabric slides over the surfaces of the form although the form is continually drawn toward the gap between the rollers by the belts and the fabric. As the fabric passes between the sides of the form and the belts, it is longitudinally compressed as the belts pass over the rollers. In this regard, the belts are formed so that the thicknesses thereof are of significant dimension relative to the diameters of the rollers, and, as a result, the linear speeds of the outer surfaces of the belts are substantially greater in the areas where the outer surfaces are stretched as they pass over the rollers than the linear speeds of the outer surfaces are in other straight sections of the belts. Accordingly, by introducing the fabric to the belts in the curved areas thereof defined by the rollers, the fabric travels initially at a relatively high rate of speed on the stretched outer surfaces of the belts, and then it travels at a relatively lower rate of speed when it reaches the straight areas of the belts, and the fabric is contracted or compressed as the outer belt surfaces return to their normal unstretched dispositions.
While apparatus of the type disclosed in the patent to Wehrmann has proven to be generally effective for longitudinally compressing tubular fabrics, it has proven to be relatively expensive to operate. Specifically, because of the way in which machines of this type have operated, they have been characterized by relatively high rates of belt wear; and, as a result, the belts of these machines have required frequent changing, and this has represented a substantial operating expense. This has been an inherent characteristic of machines of this type, because they have operated to effect compression by continually drawing a form into the nip or gap between a pair of rollers. This type of arrangement has provided relatively high uncontrollable compression pressures, and it has also caused high frictional belt wear any time that the form has accidentally engaged a belt. In particular, it has been found that high belt wear occurs particularly any time a defective area of a tubular fabric is encountered so that a portion of the fabric having one or more holes therein is compressed between the rollers with the form, whereby the form itself engages the rollers in the defective areas. As a result of the overall high belt wear rates experienced with machines of this type, and particularly as a result of belt wear caused in this manner, the belts of machines of this type have generally required changing after approximately 500 hours of use.
Safety has also been a problem with shrinkage treatment machines of the type disclosed in the aforementioned patent to Wehrmann, because they have operated with an exposed nip or gap between the rollers thereof. Specifically, instances have occurred wherein the hand of an operator has been caught in the nip or gap between a pair of rollers of a machine of this type, and before the machine could be stopped a substantial portion of the operator's arm was drawn into the machine, causing very serious injury to or, in some cases, the loss of the arm. Basically, this has been an inherent danger which has presented a substantial risk to operators of machines of this type.
The instant invention provides a novel shrinkage treatment apparatus which substantially overcomes these and other disadvantages of the heretofore known shrinkage treatment apparatus. The apparatus of the instant invention operates generally on the same basic principle as the apparatus disclosed in the Wehrmann patent, i.e., it operates by pressing a fabric into engagement with the outer surface of a curved section of a belt and then along a substantially straight section of the belt so that the fabric first travels at a relatively high rate of speed, and then at a somewhat slower rate to effect a longitudinal compression of the fabric. However, while the apparatus of the instant invention operates on this same general principle, structurally it differs substantially from the apparatus disclosed in Wehrmann, and as a result substantial advantages are provided in the apparatus of the instant invention.
The apparatus of the instant invention comprises a single continuously advancing resilient compression belt having inner and outer surfaces, a roller engaging the inner surface of the belt and defining a curved section in the extent thereof, a compression shoe which is receivable in substantially mating relation with the outer surface of the compression belt in a compression area thereof which includes at least a portion of the curved section and at least a portion of the area of the belt immediately past the curved section, and means mounting the compression shoe so that it is biased toward a position of substantially mating relation with the outer surface of the belt in the compression area. The apparatus further includes means for continuously longitudinally advancing an elongated fabric strip so that it is received in pressurized engagement between the curved belt section and the shoe and then advanced by the belt to a point in the travel thereof which is beyond the shoe. In the preferred embodiment of the apparatus, the shoe is formed of a low-friction polymer material such as tetrafluroethylene, i.e., Teflon (duPont trademark), and the shoe is resiliently biased toward the compression area with an inflatable member which is preferably pneumatically inflated to urge the compression shoe generally toward the curved section, preferably at an angle of approximately twenty degrees to the surface of the section of the belt which is immediately past the curved section. Also in the preferred embodiment, the compression shoe is slightly flexible so that it fully conforms to the configuration of the compression area to apply even pressure thereto.
For use and operation of the apparatus, an elongated fabric strip which may comprise either a single layer of fabric or a tubular strip which has been folded to a flat, two-layer configuration, is advanced to the apparatus so that it is received between the curved section of the belt and the compression shoe and so that it is advanced by the belt to a point in the travel thereof which is beyond the compression shoe. Accordingly, the fabric first travels at a relatively high rate of speed between the curved section of the belt and the compression shoe; and when the belt thereafter travels in a substantially straight direction so that the outer surface of the belt is compressed or returned to its normal disposition, the fabric which is interposed in pressurized engagement between the shoe and the belt is also compressed.
While the broad general concept of compressing a fabric by urging it into pressurized engagement with a resilient belt as the belt passes over a roller is disclosed in the aforementioned patent to Wehrmann, the apparatus of the instant invention has substantial advantages over the known apparatus. Specifically, by utilizing a single belt, a compression shoe, and a means for resiliently biasing the compression shoe towards the compression area of the belt, a controlled amount of dynamic pressure can be applied to a fabric with the shoe, and the pressure can be applied in a predetermined direction. Also, because the shoe does not have a forward portion of reduced thickness, such as the insert utilized in the apparatus of Wehrmann, it is possible for the shoe to be constructed from a more delicate low-friction material, such as Teflon (duPont TM), or some other known low-friction polymer. As a result of these features, even if the shoe engages the belt in the areas adjacent the edges of the strip or if it engages the belt inadvertently as a result of imperfections in the strip, the belt is not substantially damaged by the shoe. The chances of causing damage to the belt are even further reduced when the shoe is constructed so that it is slightly resiliently flexible whereby the shoe conforms to the configuration of the belt to assure that the pressures between the shoe and the belt are applied evenly, and this also obviously provides more uniform compression of the fabric.
As a result of these differences between the apparatus of the instant invention and the heretofore known apparatus for treating fabrics for shrinkage, a number of benefits are realized with the apparatus of the instant invention. Specifically, it has been found that the apparatus of the instant invention can effectively operate at substantially higher throughput rates than the heretofore known Wehrmann-type apparatus. Further, since the apparatus of the instant invention only utilizes a single belt, the overall cost of manufacturing the apparatus of the instant invention is approximately 40% less than the cost of manufacturing a Wehrmann-type apparatus. Further, because the apparatus of the instant invention only requires energy for driving a single belt, energy costs for operating the apparatus are reduced by as much as 50%. In addition, the belt life experienced with the apparatus of the instant invention is normally at least double the belt life experienced with the heretofore-known apparatus; and since the apparatus of the instant invention requires only a single belt instead of two belts, the overall belt expense is generally less than one fourth of the operating expense of a conventional apparatus.
In addition to these economic benefits, the apparatus of the instant invention also has substantial advantages from a safety standpoint. Substantially all of the heretofore-known Wehrmann-type apparatus for treating tubular fabrics for shrinkage have operated with dangerous open nips or gaps between the rollers thereof, and instances have occurred wherein the fingers and arms of persons have actually been drawn into machines of this kind. Accidents of this type are virtually impossible with the apparatus of the instant invention, since it operates with a single roller, and therefore it does not have an open nip area.
Further, virtually all of the heretofore-known apparatus for treating fabrics for shrinkage have been operable for treating exclusively tubular fabrics, and they have only been operative for treating tubular fabrics of different widths by changing to different-sizes of feed apparatus. On the other hand, the apparatus of the instant invention can accommodate both tubular and open-width fabrics, and the widths of fabrics can be changed while the machine is in operation since mechanical equipment changes are not required.
Accordingly, it is a primary object of the instant invention to provide an improved apparatus for treating fabrics for shrinkage.
Another object of the instant invention is to provide a shrinkage-treatment apparatus which includes a single roller and a low-friction compression shoe.
Another object of the instant invention is to provide an apparatus for shrinkage treatment of fabrics which can operate with reduced maintenance costs.
An even further object of the instant invention is to provide an apparatus which is operative for shrinkage treatment of tubular fabrics with increased safety.
A still further object of the instant invention is to provide an apparatus for shrinkage treatment of fabrics which can be used on both tubular and open-width fabrics.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.